1. Field of the Invention
The present invention relates to enzyme compositions and liquid detergent compositions. Particularly, the invention relates to enzymes which have been stabilized and to liquid laundry detergents with the stabilized enzymes.
2. Background Art
The development of detergents for the cleaning of fabric have improved steadily over the recent past. Improvements in detergent additives have included improvements of surfactants, builders, dispersing agents, fluorescent whitening agents, bleaching agents, etc. and have allowed detergents to be formulated into powders, granules and liquids. See e.g., detergents composition in U.S. Pat. Nos. 3,551,002, 3,558,498, 3,623,957, 3,749,671, 3,790,482, 3,985,686, 4,090,973, 4,011,169, 4,111,855, 4,142,999, 4,242,219, 4,261,868, 4,318,818, 4,404,115, and 4,381,247 incorporated herein by reference. Detergents compositions often contain enzymes (e.g., a protease) to aid in the degradation and removal of enzyme sensitive stains, soils and deposits. Detergent formulations which contain enzymes, however, experience the problem of decreased enzyme activity over time, especially liquid detergents which contain high levels of surfactant and water. Enzymes may hydrolyze in water and often a protease will degrade itself or other enzymes that may be present. Surfactants, for example alkyl sulfates, tend to deactivate enzymes and render them inactive. Detergent builders can sequester the calcium ion needed for enzyme stability. These problems require either an expiration date on the detergent or the undesirable alternative of an increased amount of costly enzyme being added to the detergent. There is a continuing need, therefore, for liquid detergents which contain enzymes which are stabilized and exhibit a greater activity over time. The prior art has attempted to deal with these problems.
Meister, U.S. Pat. No. 3,095,358, utilizes sorbitol to stabilize aqueous solutions containing enzymes such as papain and mixtures of protease and amylase obtained from Bacillus subtilis. This method also requires large amounts of stabilizing agent. Several patents list compounds which stabilize enzymes. However, none of the following are competitive inhibitors.
Cayle, U.S. Pat. No. 3,296,094, utilizes partially hydrolyzed and solubilized collagen and glycerol to stabilize aqueous solutions of proteolytic enzymes. This method requires large quantities of glycerol by weight of the total solution and, therefore, adds significantly to the cost of the enzyme solution.
McCarty, U.S. Pat. No. 3,557,002, uses short chain alkyl or alkoxy alkyl monohydroxy alcohols to stabilized enzyme preparations. These preparations will protect the listed enzymes at at least 50% enzyme activity after storage at 100.degree. F. for 5 weeks. Diehl, U.S. Pat. No. 4,011,169, uses aminated polysaccharides such as aminated cellulose to stabilize enzymatic activity. In U.S. Pat. No. 4,142,999, Bloching uses mono and polyvalent alcohols and ethers thereof, and an effective amount of an alkoxylated alkylamine to stabilize enzyme activity.
U.S. Pat. No. 4,261,868, Hora et al, issued Apr. 14, 1981, discloses liquid detergents containing enzymes and, as an enzyme-stabilizing system, 2-25% of a polyfunctional amino compound selected from diethanolamine, triethanolamine, diisopropanolamine, triisopropanolimine and tris(hydroxymethyl) aminomethane, and 0.25-15% of a boron compound selected from boric acid, boric oxide, borax, and sodium ortho, meta and pyroborate. The compositions can contain 10-60% surfactant, including anionics, and up to 40% builder.
U.S. Pat. No. 4,318,818, Letton et al, issued Mar. 9, 1982, discloses liquid detergents containing enzymes and an enzyme-stabilizing system comprising calcium ion and a low molecular weight carboxylic acid or salt, preferably a formate. The compositions preferably contain from about 20% to 50% surfactant, which can be anionic. In a preferred embodiment, the compositions contain about 3% to 15% of a saturated fatty acid. They are otherwise substantially free of builders, but can contain minor amounts of sequestrants.
U.S. Pat. No. 4,404,115, Tai, issued Sept. 13, 1983, discloses liquid cleaning compositions, preferably built liquid detergents, containing enzyme, 1-15% alkali metal pentaborate, 0-15% alkali metal sulfite, and 0-15% of a polyol having 2-6 hydroxy groups. The compositions can contain 1-60% surfactant, preferably a mixture of anionic and non-ionic in a weight ratio of 6:1 to 1:1, with or without soap. The compositions also preferably contain 5-50% builder.
European Patent Application 0,130,756, published Jan. 9, 1985, discloses proteolytic enzymes useful herein and methods for their preparation. The enzymes are said to be useful in laundry detergents, both liquid and granular. They can be combined with surfactants (including anionics), builders, bleach and/or fluorescent whitening agents, but there is no disclosure of specific detergent compositions.
European Patent Application 0,199,405 published Oct. 10, 1986 discloses liquid detergent compositions containing synthetic surfactants, an enzyme and boric acid or boron compound from about 0.1% to about 10%, preferably from 0.25% to 5%, and most preferably from about 0.5% to about 3%. No disclosure is made, however, of how to match the enzyme with the boric acid. As a percentage of the enzyme, the boric acid represents at least 2% up to 100,000%.
The art is illustrative of the cost and expense that has gone into stabilization of enzymes by way of adding large amounts of additional ingredients as well as the difficulties in dilution which occur due to varying teachings of the amounts of stabilizing agent which must be added based on the amount of water and other ingredient present.
It is an object of the invention therefore to stabilize enzymes and enzymes in liquid detergents with a minimum standardized amount of a stabilizer in the presence of water, detergents or other, if any, ingredients present in the liquid detergent.